CN109298503B - High precision optical wavelength reference etalon - Google Patents
High precision optical wavelength reference etalon Download PDFInfo
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- CN109298503B CN109298503B CN201710610565.5A CN201710610565A CN109298503B CN 109298503 B CN109298503 B CN 109298503B CN 201710610565 A CN201710610565 A CN 201710610565A CN 109298503 B CN109298503 B CN 109298503B
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Abstract
The high-precision optical wavelength reference etalon provided by the invention comprises: a Fabry-Perot resonant cavity; the optical compensation piece is arranged in the Fabry-Perot resonant cavity and comprises a first optical parallel flat plate and a bi-material cantilever beam supporting the first optical parallel flat plate, the bi-material cantilever beam comprises a cantilever beam main body and a thin film layer, the cantilever beam main body and the thin film layer have different thermal expansion coefficients, and an included angle between a normal of the optical compensation piece and an optical axis of the optical wavelength reference etalon can be changed when the temperature changes so as to compensate errors caused by the change of the cavity length. The optical wavelength reference etalon provided by the invention can realize high-precision compensation of the central wavelength value of the transmission peak and the wavelength temperature drift of the transmission peak of the optical wavelength reference etalon, and simultaneously realizes batch manufacturing of the optical wavelength reference etalon, thereby greatly reducing the production cost.
Description
Technical Field
The invention relates to the technical field of optics, in particular to a high-precision optical wavelength reference etalon.
Background
The optical wavelength reference etalon provides an accurate and stable optical wavelength reference standard in modern optical technology, is a key optical device in optical technologies such as spectroscopy, laser technology, optical communication, optical fiber sensing, optical precision measurement and the like, and has wide application prospect. Optical wavelength reference etalons are F-P (fabry-perot) interferometer based optical devices with periodic narrow bandwidth optical transmission peaks, also known as "optical combs," whose serialized optical transmission peak-to-peak wavelengths are commonly used as wavelength reference standards for modern optical technology. However, due to the manufacturing process deviation and the change of the environmental temperature, the wavelength drift and the wavelength precision of the optical wavelength reference etalon of the common F-P interferometer are not high, and the application requirements are difficult to meet.
High precision optical wavelength reference etalons include two implications: one is that the transmission peak wavelength and Free Spectral Range (FSR) of the optical wavelength reference etalon are kept to be accurate and consistent with the theoretical reference wavelength; the other is the stability of the transmission peak wavelength and the Free Spectral Range (FSR) of the optical wavelength reference etalon, and the factors influencing the stability are mainly the transmission peak wavelength change caused by the environmental temperature.
The traditional optical wavelength reference etalon adopts a manual processing technology, because the processing technology is difficult to accurately control the cavity length, the transmission peak wavelength deviates from the designed reference wavelength value, when the cavity length control deviation exceeds the half wavelength,the Free Spectral Range (FSR) of the optical wavelength reference etalon may also deviate from the design value, resulting in a deviation of the transmission peak wavelength of the optical etalon from the theoretical reference wavelength, affecting the wavelength reference accuracy. In order to manufacture an optical etalon with high wavelength accuracy, it is necessary to repeat high-accuracy polishing and testing, which results in very high manufacturing cost. In order to realize a highly stable optical wavelength reference etalon, which requires a resonant cavity length not varying with the ambient temperature, a "zero expansion" glass material from schottky corporation is usually used as a spacer of the optical cavity, so that although the temperature stability of the optical etalon is greatly improved, the physical expansion coefficient of the "zero expansion" glass material is not strictly equal to zero, and there is 10-7Thermal expansion coefficient/degree, and therefore does not completely compensate for the temperature drift of the wavelength.
In the optical communication technology, due to the wide application of the Dense Wavelength Division Multiplexing (DWDM) technology, there is a high requirement for the wavelength stability of the laser transmitter. In a 100G coherent optical communication system, high accuracy and stability requirements are imposed on the laser wavelength of a transmitter and the local oscillator laser of a coherent receiver, and an optical wavelength reference is required to lock the laser working wavelength. In spectroscopic analysis techniques, a high accuracy, high stability wavelength reference is required to calibrate the wavelengths of the spectrum. In optical precision measurements, high wavelength stability laser light sources are required, and these lasers are usually locked to a high accuracy, high stability wavelength reference. A high accuracy, high stability optical wavelength reference etalon is a core device in precision measurement, such as measurement of laser doppler shift (laser velocimetry), and a high stability optical etalon is required as a wavelength reference.
Optical wavelength referencing is typically accomplished with an F-P interferometer based optical wavelength reference etalon, which has a quasi-periodic series of spectral peaks, which can be visualized as a "spectral comb". All spectral peaks have a defined transmission peak center wavelength and the spacing of the center wavelengths of their adjacent transmission peaks is referred to as the Free Spectral Range (FSR). The spectrum comb is used as a wavelength reference standard in application, and strict technical requirements are provided for the wavelength accuracy, the free spectral domain size and the wavelength stability of the spectrum comb, so that the optical wavelength reference etalon is high in manufacturing process requirement, large in size, low in yield and high in cost. In the fine spectroscopic technique, even the use of "atomic filters" of known fine atomic spectroscopic structure as wavelength references is costly and the use is very limited, providing only a small number of reference wavelengths.
Optical wavelength reference etalons typically have two configurations, an "air cavity" and a "solid cavity" optical etalon. The most commonly used optical etalons are of the "air cavity" type, consisting of two parallel optical mirrors of high optical quality and an intermediate spacer. Because the optical resonant cavity is air, the refractive index of the optical resonant cavity is 1, and the influence of the air density and the component change on the refractive index can be ignored under one atmosphere, the refractive index of the air is considered not to change along with the temperature in engineering, and therefore the main factor determining the temperature change characteristic of the transmission peak wavelength is the linear temperature expansion coefficient of the intermediate spacer and is irrelevant to the thermo-optic coefficient of the material. Thus, an "air cavity" type optical wavelength reference etalon is the main solution for high stability wavelength reference filters.
In order to realize a temperature-insensitive or low-sensitive optical etalon, a "zero expansion" glass material is usually used as a spacer of the etalon, and a "zero expansion" glass of schottky company is currently used in the product. The processing of the air cavity type optical etalon adopts manual processing and single-piece manual assembly, the processing precision of the thickness of the middle spacing body is extremely high, the level of the nanometer level is reached, multiple measurement and multiple processing are needed in the processing process, and the thicknesses of the zero-expansion spacing bodies processed in a batch are inconsistent, so that the optical wavelength reference etalon in the current market is high in cost and high in price.
The solid cavity optical etalon can be used for manufacturing thin optical etalon, which directly adopts transparent optical material as an optical resonant cavity, the thickness of the optical resonant cavity is only hundreds of micrometers, the overall size is also greatly reduced, and the optical resonant cavity is only millimeter square. Factors influencing the temperature stability of the transmission peak wavelength of the solid cavity type optical wavelength reference etalon comprise the linear temperature expansion coefficient and the refractive index temperature coefficient of an optical material, and in order to realize the aim of stabilizing the transmission peak wavelength temperature, the signs of the linear temperature expansion coefficient and the refractive index temperature coefficient of the optical material must be opposite, and the sizes of the linear temperature expansion coefficient and the refractive index temperature coefficient of the optical material also need to meet a specific relation, which is very difficult to meet in the existing optical material. In order to realize the aim of temperature stabilization of the wavelength of the transmission peak, a uniaxial optical crystal is adopted, the temperature coefficient of the refractive index of the optical crystal is changed along with the incident angle of a light beam, and the optical thickness (the physical thickness of the resonant cavity is multiplied by the optical refractive index) of the optical resonant cavity can be prevented from changing along with the temperature at a special angle. The optical wavelength reference etalon can achieve the effect of wavelength temperature stabilization only for a specific polarization state of a light beam, and the cost of crystal materials is high, the processing requirement is high, and the cost of the high-precision optical etalon is very high.
Therefore, how to achieve high wavelength precision and high stability of the optical wavelength reference etalon, reduce the production cost thereof, and achieve mass production is a technical problem to be solved at present.
Disclosure of Invention
The invention provides a high-precision optical wavelength reference etalon, which is used for solving the problems of low wavelength precision and poor wavelength stability of the conventional optical wavelength reference etalon, reducing the production cost of the optical wavelength reference etalon and realizing batch production.
In order to solve the above problems, the present invention provides a high-precision optical wavelength reference etalon comprising: the Fabry-Perot resonant cavity comprises a first optical reflector and a second optical reflector which are oppositely arranged and parallel in height; the optical compensation piece is arranged in the Fabry-Perot resonant cavity and comprises an optical parallel flat plate and a bi-material cantilever beam supporting the optical parallel flat plate, the bi-material cantilever beam comprises a cantilever beam main body and a thin film layer covering the cantilever beam main body, the cantilever beam main body and the thin film layer have different thermal expansion coefficients, and an included angle between a normal of the optical compensation piece and an optical axis of the optical wavelength reference etalon can be changed when the temperature changes so as to compensate transmission wavelength deviation caused by the change of the cavity length.
Preferably, the dual-material cantilever beam comprises a first dual-material cantilever beam and a second dual-material cantilever beam, and the first dual-material cantilever beam and the second dual-material cantilever beam are symmetrically distributed on two sides of the optical parallel flat plate; the first bi-material cantilever beam comprises a first cantilever beam main body and a first thin film layer covering the first cantilever beam main body, and the first cantilever beam main body and the first thin film layer have different thermal expansion coefficients; the second double-material cantilever beam comprises a second cantilever beam main body and a second thin film layer covering the second cantilever beam main body, and the second cantilever beam main body and the second thin film layer have different thermal expansion coefficients; the deformation directions of the first dual-material cantilever beam and the second dual-material cantilever beam along with temperature change are opposite.
Preferably, the first cantilever beam main body and the second cantilever beam main body are both made of monocrystalline silicon, the first thin film layer is a silicon dioxide thin film, and the second thin film layer is an aluminum thin film.
Preferably, an initial offset angle is provided between the normal of the optical compensation plate and the optical axis of the optical wavelength reference etalon, and the initial offset angle is used for compensating the deviation of the transmission peak wavelength of the optical wavelength reference etalon and the design value.
Preferably, a patterned first optical reflecting film is plated on one side of the first optical reflecting mirror close to the second optical reflecting mirror, and a first optical antireflection film is plated on one side of the first optical reflecting mirror far away from the second optical reflecting mirror; and a patterned second optical reflecting film is plated on one side of the second optical reflecting mirror close to the first optical reflecting mirror, and a second optical antireflection film is plated on one side of the second optical reflecting mirror far away from the first optical reflecting mirror.
Preferably, the two opposite sides of the optical parallel flat plate are plated with optical antireflection films.
The principle of the optical compensation sheet is as follows: the normal direction of the optical compensation sheet and the optical waveThe included angle of the optical axis direction of the long reference etalon is the offset angle theta of the optical compensation sheet, and the offset angle can be adjusted to compensate the deviation of the optical phase of the optical wavelength reference etalon and a design value with high precision, so that the deviation of the central wavelength of the transmission peak of the optical wavelength reference etalon is compensated with high precision, and the central wavelength value of the transmission peak with high precision is realized. When the external environment temperature changes, two optical phase changes can be generated inside the optical wavelength reference etalon: one is that the Fabry-Perot resonator produces an optical phase change phi1The phase change comprises optical phase change of the optical compensation sheet along with temperature change; the other is that the bias angle theta generates a variation quantity delta theta along with the temperature variation, and the optical compensation sheet generates an optical phase variation phi along with the variation quantity delta theta of the bias angle theta2. Wherein the optical phase change phi generated by the Fabry-Perot resonant cavity1And the optical phase change phi generated by the optical compensation sheet2Of equal size and opposite direction, i.e. phi1＝-φ2Therefore, the optical phase change of the Fabry-Perot resonant cavity is compensated by the optical phase change of the optical compensation sheet, so that the whole optical phase of the optical wavelength reference etalon is not changed along with the change of the environmental temperature, namely, the central wavelength of the transmission peak of the optical wavelength reference etalon is not changed along with the environmental temperature, the wavelength stability of the optical wavelength reference etalon is improved, and the defect that the wavelength stability of the traditional optical wavelength reference etalon is seriously limited by the linear temperature expansion coefficient and the thermo-optic coefficient of an optical material is avoided. Meanwhile, the change of the offset angle of the optical compensation sheet is realized by the deformation of a bi-material cantilever beam connected with the optical parallel flat plate along with the temperature, and the bi-material cantilever beam is completely passive and manufactured based on the MEMS technology, so that the optical compensation sheet can realize batch production, and the manufacturing cost of the optical compensation sheet is greatly reduced.
According to the high-precision optical wavelength reference etalon provided by the invention, the optical compensation sheet with the double-material cantilever beam is arranged in the Fabry-Perot resonant cavity of the optical wavelength reference etalon, so that the temperature drift of the central wavelength value and the wavelength of the transmission peak of the optical wavelength reference etalon can be compensated with high precision, meanwhile, the mass production of the optical wavelength reference etalon is realized by adopting the MEMS technology, and the production cost is greatly reduced.
Drawings
FIG. 1 is a schematic diagram of the structure of a high-precision optical wavelength reference etalon according to a first embodiment of the present invention;
FIG. 2 is a schematic structural view of an optical compensatory sheet according to a first embodiment of the present invention;
FIGS. 3A-3K are major process flow diagrams of a method of fabricating a high-precision optical wavelength reference etalon according to a first embodiment of the present invention;
fig. 4 is a schematic diagram of the structure of a high-precision optical wavelength reference etalon according to a second embodiment of the present invention.
Detailed Description
The following describes in detail a specific embodiment of a high-precision optical wavelength reference etalon according to the present invention with reference to the accompanying drawings.
First embodiment
Fig. 1 is a schematic structural diagram of a high-precision optical wavelength reference etalon according to a first embodiment of the present invention. As shown in fig. 1, the high-precision optical wavelength reference etalon according to the present embodiment includes: the Fabry-Perot resonant cavity comprises a first optical reflector 11 and a second optical reflector 12 which are oppositely arranged and parallel in height; the optical compensation piece is arranged in the Fabry-Perot resonant cavity and comprises an optical parallel flat plate 13 and a bi-material cantilever beam supporting the optical parallel flat plate 13, the bi-material cantilever beam comprises a cantilever beam main body and a thin film layer covering the cantilever beam main body, the cantilever beam main body and the thin film layer have different thermal expansion coefficients, and an included angle between a normal of the optical compensation piece and an optical axis of the optical wavelength reference etalon can be changed when the temperature changes so as to compensate transmission wavelength deviation caused by the change of the cavity length of the Fabry-Perot resonant cavity. In the present embodiment, the first optical reflector 11 and the second optical reflector 12 that are highly parallel means that the parallelism between the first optical reflector 11 and the second optical reflector 12 can satisfy the requirement of constructing a fabry-perot resonator.
A patterned first optical reflecting film 112 is plated on one side of the first optical reflecting mirror 11 close to the second optical reflecting mirror 12, and a first optical antireflection film 111 is plated on one side of the first optical reflecting mirror 11 far away from the second optical reflecting mirror 12; a patterned second optical reflection film 122 is plated on one side of the second optical reflection mirror 12 close to the first optical reflection mirror 11, and a second optical antireflection film 121 is plated on one side far from the first optical reflection mirror 11. By adopting the structure of the 'air cavity', the air cavity between the first optical reflector 11 and the second optical reflector 12 forms a Fabry-Perot resonant cavity of the optical wavelength reference etalon, because the refractive index of air is 1, the influence of air density and component change on the refractive index can be ignored under one atmosphere, therefore, the refractive index of air is considered not to change along with temperature in engineering, the wavelength of the transmission peak of the optical wavelength reference etalon only changes along with the thermal expansion of the spacing body, the wavelength variation caused by the temperature change is small, and the compensation is easy.
FIG. 2 is a schematic structural view of an optical compensatory sheet according to a first embodiment of the present invention. In order to enable the optical compensation plate to perform passive optical phase compensation on the optical wavelength reference etalon, the dual-material cantilever beam in this embodiment includes a first dual-material cantilever beam 131 and a second dual-material cantilever beam 132, and the first dual-material cantilever beam 131 and the second dual-material cantilever beam 132 are symmetrically distributed on two sides of the optical parallel plate 13; the first bi-material cantilever 131 comprises a first cantilever body 1311 and a first membrane layer 1312 covering the first cantilever body 1311, the first cantilever body 1311 and the first membrane layer 1312 having different coefficients of thermal expansion; the second bi-material cantilever 132 comprises a second cantilever body 1321 and a second membrane layer 1322 covering the second cantilever body 1321, the second cantilever body 1321 and the second membrane layer 1322 have different thermal expansion coefficients; the deformation directions of the first bi-material cantilever beam 131 and the second bi-material cantilever beam 132 are opposite to each other along with the temperature change. Because the deformation directions of the first bi-material cantilever beam 131 and the second bi-material cantilever beam 132 along with the temperature change are opposite, the normal of the optical parallel plate 13 is driven to rotate when the environmental temperature changes, and the passive and automatic compensation of the optical phase of the optical wavelength reference etalon is realized. By designing the thickness, the refractive index, the offset angle and the structural parameters of the first bi-material cantilever beam and the second bi-material cantilever beam of the optical parallel plate, high-precision compensation of optical phase change caused by the cavity length change of the optical wavelength reference etalon is realized.
More preferably, the first cantilever body 1311 and the second cantilever body 1321 are each made of single crystal silicon, the first thin film layer 1312 is a silicon dioxide thin film, and the second thin film layer 1322 is an aluminum thin film. Thus, when the external environment temperature changes, the optical compensation sheet may generate S-shaped deformation as shown in fig. 2 because the deformation directions of the first bi-material cantilever beam 131 and the second bi-material cantilever beam 132 are opposite, and the optical compensation sheet may achieve the amount of change of the bias angle required by the design with the environment temperature.
The MEMS technology-based wafer-level manufacturing optical wavelength reference etalon cannot achieve high precision of the central wavelength of a transmission peak due to manufacturing and processing processes and process parameter variation distribution of different units on a wafer. In order to solve the problem, it is preferable that an initial offset angle for compensating for a deviation of a transmission peak wavelength of the optical wavelength reference etalon from a design value is provided between a normal line of the optical compensation sheet and an optical axis of the optical wavelength reference etalon in the present embodiment. The specific operation method comprises the following steps: after the optical compensation plate is inserted into the fabry-perot resonator, the offset angle is adjusted by using a precision adjusting screw 135 under the monitoring of a spectrometer, so that the offset angle reaches an initial offset angle to compensate for the wavelength deviation of the transmission peak of the optical wavelength reference etalon caused by the manufacturing process. In order to prevent damage to the optical compensation sheet, a support 136 is provided between the optical compensation sheet and the screw 135. The material of the support 136 is preferably glass because glass has a small thermal expansion coefficient.
In order to increase the light transmittance and avoid light loss, it is preferable that the optical parallel plates 13 are coated with optical antireflection films on opposite sides. As shown in fig. 1, a third optical antireflection film 133 is plated on a side of the optical parallel plate 13 facing the first optical reflector 11, and a fourth optical antireflection film 134 is plated on a side of the optical parallel plate 13 facing the second optical reflector 12.
In the high-precision optical wavelength reference etalon provided by the specific embodiment, the optical compensation sheet with the double-material cantilever beam is arranged in the Fabry-Perot resonant cavity of the optical wavelength reference etalon, so that the high-precision compensation of the central wavelength value and the wavelength temperature drift of the transmission peak of the optical wavelength reference etalon can be realized, meanwhile, the mass production of the optical wavelength reference etalon is realized by adopting the MEMS technology, and the production cost is greatly reduced.
A method of manufacturing a high-precision optical wavelength reference etalon according to the present embodiment will be described below by way of example, and fig. 3A to 3K are main process flow charts of a method of manufacturing a high-precision optical wavelength reference etalon according to a first embodiment of the present invention. As shown in fig. 3A to 3K, the method for manufacturing an optical wavelength reference etalon according to the present embodiment includes the steps of:
a) a first glass sheet is provided, and a patterned first optical reflection film 112 is plated on the upper surface of the first glass sheet to form a first optical reflection mirror 11, so that the structure shown in fig. 3A is obtained. The first glass sheet is preferably a Pyrex7740 glass sheet, and the upper surface of the first glass sheet is plated with the patterned first optical reflection film 112 based on a hard mask technology.
b) A single crystal silicon wafer is provided through which spacers 31 as shown in fig. 3B are obtained by etching. Wherein the monocrystalline silicon wafer is preferably a polished monocrystalline silicon wafer with two highly parallel sides, and the monocrystalline silicon wafer is subjected to surface oxidation, photolithography and wet etching until penetrating through the monocrystalline silicon wafer, and the oxide layer is removed to obtain the spacer 31 shown in fig. 3B.
c) And the upper surface of the first glass sheet and the first monocrystalline silicon sheet are subjected to silicon-glass bonding to form a first assembly shown in fig. 3C.
d) A second glass sheet is provided, and a patterned second optical reflection film 122 is plated on the upper surface of the second glass sheet to form a second optical reflector 12. The second glass sheet is also preferably a Pyrex7740 glass sheet, and the upper surface of the second glass sheet is plated with a patterned second optical reflection film 122 based on a hard mask technology.
e) And carrying out silicon-glass bonding on the monocrystalline silicon wafer in the first assembly and the upper surface of the second glass sheet to form a second assembly.
f) Plating a first optical antireflection film 111 on the lower surface of the first glass sheet; and plating a second optical antireflection film 121 on the lower surface of the second glass sheet to form a fabry-perot resonator structure as shown in fig. 3D. With this structure, the air cavity between the first optical mirror 11 and the second optical mirror 12 constitutes a fabry-perot resonator of the optical wavelength reference etalon.
g) An SOI monocrystalline silicon wafer is provided as an optical flat plate, the SOI monocrystalline silicon wafer is formed by sequentially laminating top silicon, a buried oxide layer 32 and a substrate 33, the top silicon is high-resistance monocrystalline silicon, and the thickness of the top silicon is tens of microns.
h) And etching the optical flat plate to form an optical parallel flat plate 13, a first cantilever main body 1311 and a second cantilever main body 1321, wherein the first cantilever main body 1311 and the second cantilever main body 1321 are symmetrically distributed on two sides of the optical parallel flat plate 13. And performing photoetching and dry etching on the top layer silicon to form the structure shown in fig. 3E, namely forming the optical parallel plate 13, the first cantilever body 1311 and the second cantilever body 1321.
i) Providing a third glass sheet, preferably a Pyrex7740 glass sheet, forming a through-middle glass sheet by laser processing to obtain a support 136, and performing silicon-glass bonding on the top silicon layer and the support to form a third composite structure as shown in fig. 3F.
j) And then the substrate 33 and the buried oxide layer 32 are completely removed by chemical mechanical polishing and thinning and silicon etching to form the structure shown in fig. 3G.
k) On the basis of the structure shown in fig. 3G, a third optical antireflection film 133 is plated on one side of the optical parallel flat plate 13; and plating a fourth optical antireflection film 134 on the other side of the optical parallel plate to form the structure shown in fig. 3H.
l) depositing a first thin film layer 1312 over the first cantilever body 1311 to form a first bi-material cantilever, the first cantilever body 1311 and the first thin film 1312 having different coefficients of thermal expansion to form the structure shown in FIG. 3I.
m) depositing a second membrane layer 1322 on the second cantilever body 1321 to form a second dual-material cantilever, wherein the second cantilever body 1321 and the second membrane 1322 have different thermal expansion coefficients to form the optical compensation plate shown in fig. 3J, and the deformation directions of the first dual-material cantilever and the second dual-material cantilever are opposite to each other with the change of temperature. Because the deformation directions of the first bi-material cantilever beam and the second bi-material cantilever beam along with the temperature change are opposite, the normal line of the optical parallel flat plate 13 is driven to rotate, so that the optical compensation sheet can generate the normal angle variation required by design along with the temperature change, and the temperature drift compensation of the optical wavelength reference etalon is realized. Preferably, the first thin film layer 1312 is a silicon dioxide thin film, and the second thin film layer 1322 is an aluminum thin film.
n) inserting the optical compensator into the Fabry-Perot resonator cavity.
o) under the monitoring of the spectrometer, adjusting the offset angle by using a precision adjusting screw 135 to make the offset angle reach an initial offset angle so as to compensate the wavelength deviation of the transmission peak of the optical wavelength reference etalon caused by the variation distribution of the process parameters of different units on the wafer and the manufacturing process, so that the wavelength of the transmission peak and the free spectral domain of the optical wavelength reference etalon accurately reach set values, and dispensing and fixing the optical compensation sheet at the initial offset angle position to form the structure shown in fig. 3K.
In the high-precision optical wavelength reference etalon provided by the specific embodiment, the optical compensation sheet with the double-material cantilever beam is arranged in the Fabry-Perot resonant cavity of the optical wavelength reference etalon, so that the high-precision compensation of the central wavelength deviation and the wavelength temperature drift of the transmission peak of the optical wavelength reference etalon can be realized, meanwhile, the mass production of the optical wavelength reference etalon is realized by adopting the MEMS technology, and the production cost is greatly reduced.
Second embodiment
Fig. 4 is a schematic structural diagram of a high-precision optical wavelength reference etalon according to a second embodiment of the present invention. For the same points of the high-precision optical wavelength reference etalon described in the first embodiment, the detailed description of the present embodiment is omitted. Differences of the present embodiment from the first embodiment are mainly described below.
As shown in fig. 4, the high-precision optical wavelength reference etalon according to the present embodiment includes: a first optical mirror 41; a second optical reflector 42, disposed opposite to the first optical reflector 41 and highly parallel to the first optical reflector 41, and forming a fabry-perot resonator with the first optical reflector 41 through a spacer; the optical compensation sheet is arranged in the Fabry-Perot resonant cavity and comprises an optical parallel flat plate 43 and a bi-material cantilever beam supporting the optical parallel flat plate 43, the bi-material cantilever beam comprises a cantilever beam main body and a thin film layer covering the cantilever beam main body, and the cantilever beam main body and the thin film layer have different thermal expansion coefficients. Due to the bi-material effect, the bi-material cantilever can drive the normal of the optical parallel plate 43 to twist when the ambient temperature changes.
In order to simplify the manufacturing process and further reduce the production cost, as shown in fig. 4, the bi-material cantilever according to the present embodiment includes a third cantilever body 4311, a third membrane layer 4312, and a fourth cantilever body 4321; the third cantilever body 4311 and the fourth cantilever body 4312 are symmetrically distributed on two sides of the optical parallel plate 43, the third thin film layer 4312 covers the third cantilever body 4311, and the third cantilever body 4311 and the third thin film layer 4312 have different thermal expansion coefficients. In this embodiment, a third bi-material cantilever 431 is formed only on one side of the optical parallel plate 43, and a third bi-material cantilever body 4311 and the thin film layer 4312 constituting the third bi-material cantilever have different thermal expansion coefficients, so that when the external temperature changes, the third bi-material cantilever can drive the normal of the optical parallel plate 43 to twist due to its own deformation, so that the offset angle of the optical compensation plate changes, and the optical phase change of the fabry-perot resonator is compensated. Compared with the first embodiment, the present embodiment forms the bi-material cantilever on only one side of the optical parallel plate 43, so that the normal torsion of the optical compensation sheet generated by the temperature change is smaller, and according to the design requirement, if the normal torsion angle of the optical compensation sheet changed by the temperature change needs to be increased, the length of the third bi-material cantilever can be increased to realize the purpose.
In this embodiment, a patterned first optical reflection film 412 may be plated on a side of the first optical reflection mirror 41 close to the second optical reflection mirror 42, and a first optical antireflection film 411 may be plated on a side far from the second optical reflection mirror 42; a patterned second optical reflection film 422 is plated on one side of the second optical reflection mirror 42 close to the first optical reflection mirror 41, and a second optical antireflection film 421 is plated on one side far from the first optical reflection mirror 41. And a third optical antireflection film 433 and a fourth optical antireflection film 434 are respectively plated on two opposite sides of the optical parallel flat plate 43. The function is the same as that of the first embodiment, and is not described in detail herein.
As with the first embodiment: after the optical compensator is inserted into the fabry-perot resonator, the offset angle is adjusted by a fine adjustment screw 435 under the monitoring of the spectrometer so that the offset angle reaches an initial offset angle. In order to prevent damage to the optical compensation sheet, a support 136 is provided between the optical compensation sheet and the screw 435.
Third embodiment
The present embodiments provide a high-precision optical wavelength reference etalon. The same points as those of the optical wavelength reference etalon described in the first embodiment or the second embodiment will not be described again in this embodiment. Differences of the present embodiment from the first embodiment or the second embodiment are mainly described below.
Compared with the first specific embodiment or the second specific embodiment, the high-precision optical wavelength reference etalon provided by the present specific embodiment further includes a second optical compensation plate, wherein the second optical compensation plate is disposed in the fabry-perot resonant cavity and includes a second optical parallel flat plate and a cantilever beam supporting the second optical parallel flat plate; and a second initial offset angle is formed between the normal of the second optical compensation sheet and the optical axis of the optical wavelength reference etalon, and the second initial offset angle is used for compensating the wavelength deviation of the transmission peak of the optical wavelength reference etalon. The second optical compensation plate and the optical compensation plate are serially inserted into the optical path of the optical wavelength reference etalon, namely, a light ray enters the Fabry-Perot resonant cavity and then respectively passes through the optical compensation plate and the second optical compensation plate. The second optical compensation plate in this embodiment is an optical compensation plate for compensating for a wavelength deviation of an optical wavelength reference etalon, and its optical material, thickness, and placement angle are carefully designed, and the position of the second optical compensation plate is adjusted to the second initial offset angle when a device is packaged, so as to compensate for a position deviation of a transmission peak center wavelength of the optical wavelength reference etalon caused by a manufacturing process deviation, and to realize compensation for a transmission peak wavelength accuracy of the optical wavelength reference etalon. In this embodiment, the optical compensation plate is an optical compensation plate with wavelength temperature drift, and the optical parallel plate is supported by a bi-material cantilever beam based on a bi-material effect, and a bias angle between a normal of the optical compensation plate and an optical axis of the optical wavelength reference etalon generates a slight angle change along with a change of an environmental temperature, so that a change of an optical path of the fabry-perot resonant cavity along with the temperature is caused to compensate for a drift of a central wavelength of a transmission peak of the optical wavelength reference etalon along with the environmental temperature, thereby realizing high-precision compensation of wavelength temperature stability of the optical wavelength reference etalon. That is, unlike the first embodiment or the second embodiment in which the optical compensation plate is used to simultaneously compensate for the wavelength temperature drift and the wavelength accuracy, in the present embodiment, the two optical compensation plates are used to respectively compensate for the wavelength accuracy and the wavelength temperature drift, and only the second initial offset angle of the second optical compensation plate needs to be adjusted during packaging, and the initial offset angle of the optical compensation plate does not need to be adjusted, that is, the normal line of the optical compensation plate in the present embodiment may be parallel to the optical axis of the optical wavelength reference etalon, so that the manufacturing and packaging processes of the compensation plate may be simplified.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (5)
1. A high-precision optical wavelength reference etalon comprising:
the Fabry-Perot resonant cavity comprises a first optical reflector and a second optical reflector which are oppositely arranged and parallel in height;
the optical compensation sheet is arranged in the Fabry-Perot resonant cavity and comprises an optical parallel flat plate and a bi-material cantilever beam for supporting the optical parallel flat plate, the bi-material cantilever beam comprises a cantilever beam main body and a thin film layer covering the cantilever beam main body, the cantilever beam main body and the thin film layer have different thermal expansion coefficients, and an included angle between a normal of the optical compensation sheet and an optical axis of the optical wavelength reference etalon can be changed when the temperature changes so as to compensate transmission wavelength deviation caused by the change of the cavity length;
the dual-material cantilever beam comprises a first dual-material cantilever beam and a second dual-material cantilever beam, and the first dual-material cantilever beam and the second dual-material cantilever beam are symmetrically distributed on two sides of the optical parallel flat plate; the first bi-material cantilever beam comprises a first cantilever beam main body and a first thin film layer covering the first cantilever beam main body, and the first cantilever beam main body and the first thin film layer have different thermal expansion coefficients; the second double-material cantilever beam comprises a second cantilever beam main body and a second thin film layer covering the second cantilever beam main body, and the second cantilever beam main body and the second thin film layer have different thermal expansion coefficients; the deformation directions of the first dual-material cantilever beam and the second dual-material cantilever beam along with temperature change are opposite.
2. The high precision optical wavelength reference etalon of claim 1, wherein the first cantilever body and the second cantilever body are both comprised of single crystal silicon, the first thin film layer is a silicon dioxide thin film, and the second thin film layer is an aluminum thin film.
3. The high precision optical wavelength reference etalon of claim 1 wherein an initial offset angle is provided between a normal to the optical compensation plate and an optical axis of the optical wavelength reference etalon, the initial offset angle being used to compensate for deviations of a transmission peak wavelength of the optical wavelength reference etalon from a design value.
4. The high-precision optical wavelength reference etalon of claim 1, wherein one side of the first optical reflector close to the second optical reflector is plated with a patterned first optical reflective film, and one side of the first optical reflector far away from the second optical reflector is plated with a first optical anti-reflection film; and a patterned second optical reflecting film is plated on one side of the second optical reflecting mirror close to the first optical reflecting mirror, and a second optical antireflection film is plated on one side of the second optical reflecting mirror far away from the first optical reflecting mirror.
5. The optical wavelength reference etalon of claim 1 wherein opposing sides of the optical parallel plates are coated with optical antireflection coatings.
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| CN102081243A (en) * | 2010-12-08 | 2011-06-01 | 福州高意光学有限公司 | Tuning method for optic tunable filter |
| CN102893212A (en) * | 2010-03-24 | 2013-01-23 | 元博科技有限公司 | Reflective display using calibration data for electrostatically maintaining parallel relationship of adjustable-depth cavity components |
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| CN104698584A (en) * | 2015-03-30 | 2015-06-10 | 上海新微技术研发中心有限公司 | Double-beam type thermally-driven tunable filter and manufacturing method thereof |
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| US7061681B2 (en) * | 2004-03-02 | 2006-06-13 | Hewlett-Packard Development Company, L.P. | Fabry-Perot interferometer |
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| CN102893212A (en) * | 2010-03-24 | 2013-01-23 | 元博科技有限公司 | Reflective display using calibration data for electrostatically maintaining parallel relationship of adjustable-depth cavity components |
| CN102081243A (en) * | 2010-12-08 | 2011-06-01 | 福州高意光学有限公司 | Tuning method for optic tunable filter |
| CN103293660A (en) * | 2013-05-31 | 2013-09-11 | 华中科技大学 | Miniature F-P (Fabry-Perot) cavity tunable filter and method for manufacturing same |
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